linux-kernel - Re: [RFC] asm-generic/tlb: stub out pmd_free_tlb() if __PAGETABLE_PMD

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Message-ID: <20191014214802.GA32665@bombadil.infradead.org>
Date:   Mon, 14 Oct 2019 14:48:02 -0700
From:   Matthew Wilcox <willy@...radead.org>
To:     Linus Torvalds <torvalds@...ux-foundation.org>
Cc:     Vineet Gupta <vineetg76@...il.com>,
        linux-arch <linux-arch@...r.kernel.org>,
        Arnd Bergmann <arnd@...db.de>,
        Peter Zijlstra <peterz@...radead.org>,
        "Aneesh Kumar K . V" <aneesh.kumar@...ux.ibm.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Nick Piggin <npiggin@...il.com>, Linux-MM <linux-mm@...ck.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        linux-snps-arc@...ts.infradead.org, Will Deacon <will@...nel.org>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>
Subject: Re: [RFC] asm-generic/tlb: stub out pmd_free_tlb() if
 __PAGETABLE_PMD_FOLDED

On Mon, Oct 14, 2019 at 01:38:34PM -0700, Linus Torvalds wrote:
> And now I've said pgd/pud/p4d/pmd so many times that I've confused
> myself and think I'm wrong again, and I think that historically -
> originally - we always had a pgd, and then the pmd didn't exist
> because it was folded into it. That makes sense from a x86 naming
> standpoint. Then x86 _did_ get a pmd, and then we added more levels in
> between, and other architectures did things differently.

Oh my goodness.  Thank you for writing all this out and finally getting
to this point.  I was reading the whole thing thinking "This is different
from what I remember" and then you got here.  This explains so much about
how our MM does/doesn't work, and it's not just me that's confused ;-)